The present invention relates generally to a printing system and, more particularly, to the control of an ink drop printing system based on the ink to be deposited on each page to be printed.
In printing systems in which images are printed by depositing drops of ink onto a sheet of paper, such as ink jet printers, drying the ink which has been deposited upon a sheet of paper presents a problem. This is the case since such printers generally use a water base ink and deposit a substantially greater volume of ink in forming a print image than do other types of printers. It is desirable to rapidly dry the ink in a small dryer section of the printer utilizing a minimum amount of energy. In an office environment, reduced space and energy requirements are particularly important.
An illustrative ink drying system for an ink jet printer is described in the September, 1979 issue of Research Disclosure as Disclosure No. 18508. In the disclosed drying system, air surrounding the sheet of copy paper is drawn through a bed of hygroscopic material to remove moisture from the air. The dried air is then heated by passing it through an electronic subsystem which controls the ink jet printer and an illumination subsystem of the printer. The dried and heated air is then blown at high velocity onto a printed sheet of paper to accelerate drying of the ink deposited thereon. The hygroscopic material is regenerated by heaters within the bed which heat the material when the printer is not in operation to thereby remove moisture from the bed.
The drying system, as disclosed, may also require supplemental heating by means of quartz lamps or otherwise. The supplemental heating typically is needed only for drying copies which have a large amount of ink deposited thereon. A detector arrangement may be provided to determine the amount of ink used for printing the largest solid ink covered area to produce a control signal which is used to switch on the supplemental heating only as needed. The detector control signal may also be used to slow the speed of travel of the copy paper through the drying section of the printer when a large amount of ink has been deposited upon a paper sheet.
While the disclosed sheet dryer for an ink jet printer is highly efficient, it accommodates increased drying requirements by means of supplemental heating and ultimately by also slowing the speed of travel of the copy paper through the dryer. Both of these measures are undesirable. Supplemental heating requires additional energy input and a slowed paper speed may complicate the printing process. Since the paper path through the dryer is typically a portion of a continuous path including the transportation of the paper past the ink jet printing apparatus, a speed reduction requires adjustment of the rather complex control of the ink jet printer. Therefore, it is desirable to maintain a constant speed through the dryer/printer section to simplify the control of the ink jet printer.
It is, thus, apparent that the need exists for an improved method and apparatus for controlling an ink jet printer to facilitate drying of printed paper sheets while neither interfering with the printing operation nor requiring supplemental heating devices.